Various methods have been used for the preparation of synthetic leather which include, for example, dyeing, the treatment with a gravure coater or knife coater, or using a release sheet and the like. Among these, a method of using a release sheet is carried out in the following manner. A release sheet is provided in advance in which the desired uneven pattern is formed on the surface having releasability. A raw resin for synthetic leather is then applied on a release resin layer of the release sheet. After dried and solidified, the resin layer is released from the sheet. In a process for the preparation of synthetic leather using such a release sheet, there is a need for providing the same number of release sheets as that of the uneven designs to be applied on the synthetic leather.
Recently, with a wide variety of uses of synthetic leather, various kinds and small lots have been required in the preparation process. Although the requirement for various kinds may be satisfied by preparing various release sheets with various uneven designs, it is difficult to satisfy the requirement for small lots because a release sheet to be used should be changed every uneven designs and, therefore, the preparatory time for the preparation increases and using efficiency of raw materials is lowered. Alternatively, it may also be considered that a release sheet on which at least two uneven patterns are formed in advance is prepared to satisfy the requirement for small lots. In such a case, there is, however, a problem that it is difficult to satisfy the requirement for various kinds. Furthermore, it is also required to lower the costs for release sheets in order to satisfy the requirement for various kinds and small lots in the preparation of synthetic leather. However, there is a limit in lowering the costs for the preparation process using the prior art release sheets where a release resin layer with an uneven pattern is provided on the base material.
The present invention has been done in such circumstances. The present invention provides a release sheet in which various uneven designs can be formed in the desired amount and a process for the preparation of synthetic leather using this release sheet in which synthetic leather can easily be prepared in various kinds and small lots and it is possible to lower the costs.